The present invention is directed toward electrical transfer components between a rotary member and a stator member. FIG. 1 and FIG. 2 contain an example of a rotary member 12 and a stator member 14. In an application such as the radar for a ship, the rotary member 12 is in a constant state of rotation about an axis. The stator member 14 may be an object that completely encircles the rotary member 12, as shown in FIG. 1 and FIG. 2, or it may be located on only one side of the rotary member 12. In either case, the stator member 14 is proximate to the rotary member 12 at a substantially constant distance.
The rotary member 12 and stator member 14 may be capable of transferring low voltage signals as well as power. The rotary member 12 and stator member 14 may transfer a plurality of circuits. In the embodiment shown in FIG. 1 and FIG. 2, rotary contacts 16 are axially stacked in the rotary member 12 such that electrical contact can be made with each of the rotary contacts 16 at any point along the circumference of the rotary member 12. A corresponding number of stator conductors 18 are run to the stator member 14, such that when an electrical transfer component is installed between the rotary member 12 and the stator member 14, current flows between the rotary contacts 16 and the stator conductors 18. A special type of electrical connector is then needed to transfer electrical current between the rotary member 12 and the stator member 14. A slip ring 20, shown in FIG. 3, is one such electrical connector.
Slip rings 20 have a long history of applications for the transfer of electrical energy between, a stator member 14 and a rotary member 12. This transfer is affected by conducting the electrical signals and power from one member to the other member through a sliding contact 22. Typically, the sliding contact 22 is a conductive brush that is firmly mounted to the stator member 14 and maintains electrical contact with the rotary member 12 by sliding along one of the rotary contacts 16. This electrical connection technique achieves sliding electrical interface configurations for both low level signals and for power transfer. However, the regular and constant use, required for many transfer components connecting stator and rotary members, results in significant wear and tear on the sliding contact 22 over short periods of time. Therefore, even properly operating slip rings require constant maintenance at significant expense.
The large variety of electrical transfer requirements, specified by the broad field of users, introduces another problem for sliding transfer, which has both design and cost ramifications. Each new design of the transfer mechanism requires new tooling, fixtures, and molds. This demand of new designs results in long delivery schedules from definition to unit delivery as well as increased manufacturing costs. Since envelope parameters of diameter, length and shape as well as performance requirements of voltage, current, waveform, frequency and electrical resistance noise (or signal quality) establish many of the design requirements of the transfer unit, each application configuration and design is unique. This situation identifies why new non-recurring design and tooling costs accrue with each new set of specifications. Ideally, a new transfer mechanism would be designed that could be retrofitted to existing transfer mechanisms cost effectively.
One design configuration of the rotary member consists of stacked sets of rings and spacers to form an axial series of single non-shielded circuits. This design provides annulus channels for rolling interconnection balls, in lieu of brushes, between the inner and the outer circuit rings. This configuration provides for repeated use of common contact rings and spacers and the elimination of a molding process, which can effect cost reductions, the leads must be attached, and the rings machined and plated, individually. The labor associated with handling individual components drives the cost of production upward. Additionally, the cost of the configuration is adversely affected by the labor required to feed the lead wires through the individual rings and spacers during the assembly process. The assembly complexity and associated high manufacturing cost of the described configuration is particularly apparent for transfer units that require more than one hundred circuits.
Additionally the greater wear debris of slip rings exacerbates an electrical insulative breakdown problem of adjacent circuits when adequate barriers are not provided. When a rotary transfer mechanism is used in severe environmental conditions, even wiper seals built into the housings are not able to prevent a measure of moisture and contaminants from entering the unit. These contaminants combined with wear debris from the slip rings often results in electrical bridging between adjacent circuits and electrical insulative failure of the unit if adequate barriers are not provided. Circuit barriers are difficult to mold or machine into the module without breakage because of the small axial thickness which is available in the design. In addition, the barrier must be formed from the same insulating plastic material the rings are set in which results in a brittle, and easily damaged, protective wall.
Thus, a heretofore unaddressed need exists in the industry to address the aforementioned deficiencies and inadequacies.